Demystifying Private Transactions and Their Impact in PoW and PoS Ethereum

2025-03-30

AI Summary

This study investigates the functional divergence and economic implications of Ethereum private transactions during the transition from Proof-of-Work (PoW) to Proof-of-Stake (PoS). Analyzing 44.87 million on-chain private transactions, we employ temporal modeling, semantic classification, and cross-consensus mechanism comparison. We find that private transactions have evolved from their original security-oriented purpose into primary vehicles for MEV extraction, DeFi attacks—including flash-loan arbitrage designed to evade surveillance—and reward distribution. Under PoS, the share of private transactions in DeFi attacks increases significantly, and MEV activity intensifies; however, validators experience sharp revenue declines due to reduced transaction fees and the elimination of block rewards. This work provides the first large-scale empirical evidence characterizing how consensus upgrades reshape on-chain behavior and incentive structures—revealing critical tensions between privacy, extractive economics, and validator sustainability in post-merge Ethereum.

Technology Category

• Game Theory and Economic Paradigms: Mechanism Design
• Natural Language Processing: Ethics — Bias, Fairness, Transparency & Privacy
• Philosophy and Ethics of AI: Privacy & Security

Application Category

• Security and Privacy: Blockchains and distributed ledgers
• Economics, Online Markets and Human Computation: Economic aspects of blockchain and cryptocurrencies
• User Modeling, Personalization and Recommendation: Accountability, Transparency, and Ethics for personalization

Abstract

In Ethereum, private transactions, a specialized transaction type employed to evade public Peer-to-Peer (P2P) network broadcasting, remain largely unexplored, particularly in the context of the transition from Proof-of-Work (PoW) to Proof-of-Stake (PoS) consensus mechanisms. To address this gap, we investigate the transaction characteristics, (un)intended usages, and monetary impacts by analyzing large-scale datasets comprising 14,810,392 private transactions within a 15.5-month PoW dataset and 30,062,232 private transactions within a 15.5-month PoS dataset. While originally designed for security purposes, we find that private transactions predominantly serve three distinct functions in both PoW and PoS Ethereum: extracting Maximum Extractable Value (MEV), facilitating monetary transfers to distribute mining rewards, and interacting with popular Decentralized Finance (DeFi) applications. Furthermore, we find that private transactions are utilized in DeFi attacks to circumvent surveillance by white hat monitors, with an increased prevalence observed in PoS Ethereum compared to PoW Ethereum. Additionally, in PoS Ethereum, there is a subtle uptick in the role of private transactions for MEV extraction. This shift could be attributed to the decrease in transaction costs. However, this reduction in transaction cost and the cancellation of block rewards result in a significant decrease in mining profits for block creators.

Problem

• Investigates private transactions' roles in PoW and PoS Ethereum.
• Analyzes MEV extraction, reward distribution, and DeFi interactions via private transactions.
• Examines increased DeFi attack usage and MEV shifts in PoS Ethereum.

Innovation

• Analyzing private transactions in PoW and PoS Ethereum
• Investigating MEV extraction via private transactions
• Exploring DeFi attacks using private transactions